The study of correlation among different scattering parameters in an aggregate dust model

Abstract

We study the light scattering properties of aggregate particles in a wide range of complex refractive indices ($m = n + i k$, where $1.4 \le n \le 2.0$, $0.001 \le k \le1.0$) and wavelengths ($0.45 \le \lambda\le1.25 \mbox{ }\upmu \mbox{m}$) to investigate the correlation among different parameters e.g., the positive polarization maximum ($P_{\mathrm{max}}$), the amplitude of the negative polarization ($P_{\mathrm{min}}$), geometric albedo ($A$), $(n,k)$ and $\lambda$. Numerical computations are performed by the Superposition T-matrix code with Ballistic Cluster–Cluster Aggregate (BCCA) particles of 128 monomers and Ballistic Aggregates (BA) particles of 512 monomers, where monomer’s radius of aggregates is considered to be 0.1 μm. At a fixed value of $k$, $P_{\mathrm{max}}$ and $n$ are correlated via a quadratic regression equation and this nature is observed at all wavelengths. Further, $P_{\mathrm{max}}$ and $k$ are found to be related via a polynomial regression equation when $n$ is taken to be fixed. The degree of the equation depends on the wavelength, higher the wavelength lower is the degree. We find that $A$ and $P_{\mathrm{max}}$ are correlated via a cubic regression at $\lambda= 0.45\mbox{ }\upmu \mbox{m}$ whereas this correlation is quadratic at higher wavelengths. We notice that $|P_{\mathrm{min}}|$ increases with the decrease of $P_{\mathrm{max}}$ and a strong linear correlation between them is observed when $n$ is fixed at some value and $k$ is changed from higher to lower value. Further, at a fix value of $k$, $P_{\mathrm{min}}$ and $P_{\mathrm{max}}$ can be fitted well via a quartic regression equation when $n$ is changed from higher to lower value. We also find that $P_{\mathrm{max}}$ increases with $\lambda$ and they are correlated via a quartic regression.